Telemanipulators with Sensor/Actuator Asymmetries Fail the Robustness Criterion

Force reflection in telemanipulators can be challenging and costly, often prohibitively so. By reducing the number of sensors and actuators used in the telemanipulator and providing the user only partial force feedback, cost and performance concerns can be optimized. While partial force feedback is beneficial practically, it creates a sensor/actuator asymmetry in the device. Robust stability for systems with sensor/actuator asymmetries has not been examined previously. We show that telemanipulators with sensor/actuator asymmetries are not passive and do not satisfy the robustness stability criterion. Thus, they are potentially unstable. Further, we motivate the need for additional stability criterion for telemanipulators that are not passivity-based.